Apparatus for the processing of photographic sheet material

ABSTRACT

An apparatus, having relatively low capital cost, for the processing of photographic sheet material (22) comprises a plurality of closed treatment cells (12 1 , 12 2 , 12 3 , 12 4 ) and a sheet material path (20) extending through the cells in sequence. A following cell (12 3 ) has a treatment liquid inlet (40) and a treatment liquid outlet (42). The treatment liquid outlet (42) is connected to a treatment liquid inlet (44) of a preceding cell (12 2 ) by way of a connecting passage (46). A single pump (48) is sufficient to transfer treatment liquid through the cells.

FIELD OF THE INVENTION

This invention relates to an apparatus for the processing ofphotographic sheet material, such as X-ray film, pre-sensitised plates,graphic art film and paper, and offset plates. In particular theinvention relates to such an apparatus comprising a plurality of closedtreatment cells and means defining a sheet material path through thecells in sequence, and to a method of processing photographic sheetmaterial in such an apparatus.

BACKGROUND OF INVENTION

As a rule, a processing apparatus for photographic sheet materialcomprises several vessels each of which contains a treatment liquid,such as a developer, a fixer and a rinse liquid. As used herein, theterm sheet material includes not only photographic material in the formof cut sheets, but also in the form of a web unwound from a roll. Thesheet material to be processed is transported through these vessels inturn, by transport means such as one or more pairs of drive rollers, andthereafter optionally to a drying unit. The time spent by the sheetmaterial in each vessel is determined by the transport speed and thedimensions of the vessel in the sheet feed path direction.

In a conventional processing apparatus the sheet material is transportedalong a generally horizontal feed path, the sheet material passing fromone vessel to another usually via a circuitous feed path passing underthe surface of each treatment liquid and over dividing walls between thevessels. However, processing machines having a substantially verticalorientation have also been proposed, in which a plurality of vessels aremounted one above the other, each vessel having an opening at the topacting as a sheet material inlet and an opening at the bottom acting asa sheet material outlet or vice versa. U.S. Pat. No. 4,166,689(Schausberger et al. assigned to Agfa-Gevaert AG) describes such anapparatus.

It is known in the art to perform the rinsing of a silver halidephotographic material which has been developed and fixed, by means of a"cascades" rinsing station which comprises two or more rinsing tanksthrough which the material is passed in succession, the rinsing liquidflowing in counter-current. The advantage is that the last rinsing tankwill contain almost fresh rinsing water so that silver effluent will besmall. Cascade processing of sheet materials with other processingliquids, such as developers or fixers, also has advantages.

Such a cascade rinsing arrangement is known in which a pump is providedfor feeding liquid to the last cell and further pumps are provided fortransferring liquid from each cell to its preceding cell. The provisionof a pump between each pair of adjacent cells is costly, especiallybearing in mind that such pumps represent a significant proportion ofthe cost of the total apparatus.

While the use of pumps in a horizontal processing apparatus can beavoided by an overflow cascade, liquid levels would be different indifferent cells and difficult to control in view of surface effects.

OBJECTS OF INVENTION

It is an objective of the present invention to provide an apparatus forthe processing of photographic sheet material where the number of pumpsused in the apparatus can be significantly reduced while maintaining theadvantages of cascade processing.

SUMMARY OF THE INVENTION

We have discovered that this and other useful objects can be realised bythe use of closed cells in addition to the provision of a connectingpassage leading from a following cell to a preceding cell.

According to a first aspect of the invention there is provided anapparatus for the processing of photographic sheet material comprising aplurality of treatment cells and means defining a sheet material paththrough the cells in sequence, characterised in that a following one ofthe cells has a treatment liquid inlet and a treatment liquid outlet,the treatment liquid outlet being connected to a treatment liquid inletof a preceding one of the cells by way of a connecting passage and inthat at least the following cell is a closed cell.

In another aspect, the invention provides a method of processing ofphotographic sheet material comprising passing the sheet material alonga sheet material path in sequence through a plurality of treatmentcells, characterised by feeding treatment liquid to a treatment liquidinlet of a closed following one of the cells and passing the treatmentliquid from a treatment liquid outlet of the closed following cell to atreatment liquid inlet of a preceding one of the cells by way of aconnecting passage.

The following treatment cell, and preferably all the treatment cells inthe cascade, are closed. Not only does this feature reduce evaporation,oxidation and carbonisation of the treatment liquid, it also enables thenumber of pumps and sensors which need to be used with the apparatus tobe significantly reduced. In an embodiment of the invention, a treatmentliquid pump is connected to the inlet of the following cell to causeflow of treatment liquid in sequence through the following cell, throughthe connecting passage and through the preceding cell. Thus the need fora pump between each cell is avoided, since provided that the cells areclosed, one pump for each treatment liquid is sufficient to ensure flowthrough all the cells.

The apparatus according to the invention may further comprise means toensure the filling of at least the preceding cell with treatment liquidto a predetermined level, such as a liquid level sensor associated withat least the preceding cell. Only one such sensor is required, since thepreceding cell is filled with treatment liquid after the following cellhas been filled. The predetermined level of treatment liquid in thefollowing cell may be defined, for example, by the position of thetreatment liquid outlet. Where any cell is not a closed cell, it wouldbe preferable to provide a liquid level sensor in each cell, so as toenable proper compensation for the loss of liquid therefrom byevaporation. For this reason we prefer that all cells in the apparatusbe closed.

The preceding cell will usually be that cell which immediately precedesthe following cell, although it is possible to provide one or morefurther cells between the following cell and the preceding cell ifdesired.

The connecting passage may be formed within a wall of the housing of theapparatus or may be constituted by additional pipework. Preferably, thepassage, at least along part of its length, is narrow enough to limitthe reverse flow of treatment liquid from the preceding cell to thefollowing cell when the pump is not operating. However, the passageshould not be so narrow as to significantly restrict the flow oftreatment liquid in the operational direction when the pump isoperating. A one-way valve may be provided in the connecting passage tofurther limit the reverse flow of treatment liquid when the pump is notoperating.

Each cell preferably comprises a housing within which is mounted arotatable roller biased towards a reaction surface to define a rollernip there-between through which the sheet material path extends. In suchan arrangement, each cell may further comprise associated sealing meansserving to provide a gas- and liquid-tight seal between the roller andreaction surface on the one hand and the housing on the other. Thetreatment liquid outlet of the following cell is preferably so locatedas to ensure that the roller and the reaction surface are wetted bytreatment liquid in the following cell. This provides the advantage thatthe maximum film path length is used for processing, and the depositionof salts on the roller and reaction surface during stand-by is reduced.Arranging for the roller and the reaction surface to be constantlywetted by the treatment liquid is preferred when the treatment liquidsin adjacent cells are identical or compatible.

In one possible arrangement for the apparatus, the cells are mounted oneabove the other in a stack to define a substantially vertical sheetmaterial path through the apparatus. In the present context, the term"substantially vertical" is intended to mean that the sheet materialmoves along a path from the inlet to the outlet which is either exactlyvertical, or which has a vertical component greater than any horizontalcomponent. The use of a vertical orientation for the apparatus leads toa number of advantages. In particular the apparatus occupies only afraction of the floor space which is occupied by a conventionalhorizontal arrangement. Furthermore, the sheet transport path in avertically oriented apparatus may be substantially straight, in contrastto the circuitous feed path which is usual in a horizontally orientedapparatus. The straight path is independent of the stiffness of thesheet material and reduces the risk of scratching compared with ahorizontally oriented apparatus. In a vertical apparatus, the followingcell may be above or below the preceding cell, depending on thedirection of the sheet material transport path.

In an alternative configuration, the cells are mounted one beside theother to define a substantially horizontal sheet material path throughthe apparatus.

The invention is applicable to any treatment liquid, in particulartreatment liquids selected from photographic sheet material developer,photographic sheet material fixer, and wash water. The apparatus andmethod described herein can be used to process a number of differenttypes of photographic sheet material, including for example X-ray film,one- and two-sheet DTR sheet materials, lithographic plates and graphicarts sheet materials, the details of the apparatus being modified asdesired according to the intended use.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described by the following illustrativeembodiments with reference to the accompanying drawing without theintention to limit the invention thereto, and in which:

FIG. 1 is a cross-sectional view of two cells of a vertical processingapparatus according to the invention, with adjacent cells being partlyshown.

As shown in FIG. 1, an apparatus for the processing of photographicsheet material comprising a number of closed treatment cells 12¹, 12²,12³, 12⁴. The cells are mounted one above the other in the stack todefine the substantially vertical sheet material path 20 through thecells in sequence, the sheet material 22 moving in a downwards directionas indicated by the arrow A. The cells may be of a modular structure ormay be part of an integral apparatus as shown. The treatment cells 12¹,12², 12³, 12⁴ are closed.

Only part of the apparatus is shown in FIG. 1. The cell 12¹ which isonly partly shown is for example a developing cell. Cells 12² and 12³represent a cascade of fixing cells in which the developed sheetmaterial is fixed. The cascade as shown consists of only two cells butfurther cells could be added as desired. The first fixing cell 12² isreferred to herein as the preceding cell, the second fixing cell 12³ asthe following cell. Cell 12⁴ which again is only partly shown,represents a washing cell, or the first of a cascade of washing cells.The liquid in the washing cell 12⁴ is preferably not in contact with therollers of that cell.

Each cell comprises a housing 14 within which is mounted a firstrotatable roller 28 biased towards the reaction surface in the form of asecond rotatable roller 30 to define the roller nip 36 there-betweenthrough which the sheet material path 20 extends. Each roller 28, 30 isof the squeegee type comprising a stainless steel hollow core 32carrying an elastomeric covering 34. The core 32 is in cylindrical formhaving constant internal and external diameters along the lengththereof. The rollers 28, 30 are biased towards each other with a forcesufficient to effect a liquid tight seal but without causing damage tothe photographic sheet material 22 as it passes there-between. The lineof contact between the roller surfaces 29 and 31 defines the nip 36. Thesheet material preferably has a width which is at least 10 mm smallerthan the length of the nip, so as to enable a spacing of at least 5 mmbetween the edges of the sheet and the adjacent limit of the nip 36,thereby to minimise leakage. The rollers 28, 30 are coupled to drivemeans (not shown) so as to constitute drive rollers for driving thesheet material 22 along the sheet material path 20.

Each cell further comprises associated sealing members diagrammaticallyindicated at 38 and 39, the sealing members being secured to the housing14 and serving to provide the gas- and liquid-tight seal between therollers 28, 30 on the one hand and the housing 14 on the other. Thetreatment liquid 24 is therefore retained in each cell by the rollers28, 30 and the sealing members 38, 39. Thus, treatment liquid from cell12² is prevented from falling into the lower cell 12³ by the rollers 28,30 and sealing members 38, 39, while vapours from the lower cell 12³ areprevented from entering the cell 12² or escaping into the environment.This construction has the advantage that the treatment liquid in any onecell is not contaminated by contents of the adjacent cells and that byvirtue of the treatment liquids being in a closed system evaporation,oxidation and carbonisation thereof is significantly reduced (and anyother undesirable exchange between the treatment liquid and theenvironment).

The following cell 12³ has a treatment liquid inlet 40 and a treatmentliquid outlet 42, the treatment liquid outlet 42 being connected to atreatment liquid inlet 44 of the immediately preceding cell 12² by wayof a connecting passage 46. The connecting passage 46 is constituted byadditional pipework.

A treatment liquid pump 48 is connected to the inlet 40 of the followingcell 12³ to cause flow of treatment liquid 24 in sequence through thefollowing cell 12³, through the connecting passage 46 and through thepreceding cell 12². The passage 46 is narrow enough to limit the reversediffusion from the preceding cell 12² to the following cell 12³ when thepump 48 is not operating. However, the passage 46 is not so narrow as tosignificantly restrict the flow of treatment liquid 24 in theoperational direction when the pump 48 is operating. As shown, thetreatment liquid inlet 44 of the preceding cell 12², is below the level26 of treatment liquid therein. It is also possible to place the inlet44 above the level 26, such an arrangement leading to the advantage thatreverse diffusion is prevented.

The treatment liquid outlet 42 of the following cell 12³ is located asto ensure that the rollers 28, 30 are wetted by treatment liquid 24 inthe following cell 12³.

The preceding cell 12² also has a treatment liquid outlet 50. A liquidlevel sensor 52, connected to the outlet 50 of the preceding cell 12²ensures the filling of the preceding cell 12² and the following cell 12³with treatment liquid 24 to predetermined levels.

The predetermined level 25 of treatment liquid 24 in the following cell12³ is defined by the position of the treatment liquid outlet 42. Thepredetermined level 26 of treatment liquid 24 in the preceding cell 12²is defined by the position of the treatment liquid outlet 50.

In use photographic sheet material 22 is passed along the sheet materialpath 20 in sequence through the closed treatment cells 12¹, 12², 12³,12⁴. Treatment liquid 24, in this case a fixing solution, is fed to thetreatment liquid inlet 40 of the following cell 12³. The treatmentliquid 24 is passed, under force of the pump 48, from the treatmentliquid outlet 42 of the following cell 12³ to the treatment liquid inlet44 of the preceding cell 12² by way of the connecting passage 46.

In a modification, the rollers 28, 30 may be mounted in such a manner asto be capable of being moved away from each other. Such a modifiedapparatus may be cleaned periodically by using the pump 48 to pump acleaning liquid, such as water, into the cells and then moving therollers of each pair 28, 30 away from each other to allow the cleaningliquid to drain from the apparatus, or from selected cells thereof.

In an alternative configuration, the cells are mounted one beside theother to define the substantially horizontal sheet material path throughthe apparatus.

What is claimed is:
 1. An apparatus for the processing of photographicsheet material (22) comprising a plurality of treatment cells (12¹, 12²,12³, 12⁴) defining a sheet material path (20) through said cells insequence, wherein a following one of said cells (12³), has a treatmentliquid inlet (40) and a treatment liquid outlet (42), said treatmentliquid outlet (42) being connected to a treatment liquid inlet (44) of apreceding one of said cells (12²) by way of passage (46), characterizedin that at least the following cell (12³) is a closed cell and in thatmeans are provided to ensure the filling of at least said preceding cell(12²) with treatment liquid (24) to a predetermined level (26), saidmeans comprising a liquid level sensor (52) associated with at leastsaid preceding cell (12²).
 2. An apparatus according to claim 1, whereina treatment liquid pump (48) is connected to the inlet (40) of saidfollowing cell (12³) to cause flow of treatment liquid (24) in sequencethrough following cell (12³), through said connecting passage (46) andsaid preceding cell (12²).
 3. An apparatus according to claim 1, whereinsaid preceding cell (12²) immediately precedes said following cell(12³).
 4. An apparatus according to claim 1, wherein each cell comprisesa housing (14) within which is mounted a rotatable roller (28) biasedtowards a reaction surface (30) to define a roller nip (36)there-between through which said sheet material path (20) extends.
 5. Anapparatus according to claim 4, wherein each cell further comprisesassociated sealing means (38, 39) serving to provide a gas- andlight-tight seal between said roller (28) and said reaction surface (30)on the one hand and said housing (14) on the other.
 6. An apparatusaccording to claim 1, wherein said cells (12¹, 12²,2⁴) are mounted oneabove the other in a stack to define a substantially vertical sheetmaterial path (20) through the apparatus.
 7. An apparatus according toclaim 5, wherein said treatment liquid outlet (42) of said followingcell (12³) is so located as to ensure that said roller (28) and saidreaction surface (30) are wetted by treatment liquid (24) in saidfollowing cell (12³).
 8. An apparatus according to claim 1, wherein saidcells (12¹, 12²,) are mounted one beside the other to define asubstantially horizontal sheet material path (20) through the apparatus.9. A method of processing photographic sheet material comprising passingsaid sheet material (22) along a sheet material path (20) in sequencethrough a plurality of treatment cells (12¹, 12², 12³ 12⁴), feedingtreatment liquid (24) to a treatment liquid inlet (40) of a closedfollowing one of said cells (12³) and passing said liquid (24) from atreatment liquid outlet (42) of said closed following cell (12³) to atreatment liquid inlet (44) of a preceding one of said cells (12²) byway of a connecting passage (46), characterized by ensuring the fillingof at least said preceding cell (12²) with treatment liquid (24) to apredetermined level (26), by using a liquid level sensor (52) associatedwith at least said preceding cell (12²).
 10. A method according to claim9, wherein said treatment liquid (24) is selected from photographicsheet material developer, photographic sheet material fixer, and washwater.